Pressure gauge for pneumatic tires



June 1930- J. E. KENNEDY I PRESSURE GAUGE FOR PNEUMATIC TIRES Filed July 26, 1927 Patented June 3, 1930 I l UNITED STATES PATENT, OFFICE JOHN E. KENNEDY, OF LOS ANGELES, CALIFORNIA PRESSURE GAUGE FOR ENEUMATIG TIRES Application filed July 26, 1927. Serial No. 208,435..

This invention relates to pressure gauges With a view to meeting these practical particularly adapted 'to be applied to pneudifliculties in the art the resent improvement matic tire stems temporarily for the purpose has been devised whic consists generally of testing the tire pressure, and is in the naspeaking, in a combination with a hollow casture of an improvement upon the ]OiI1t appliing adapted to be applied to the valve stem of 55 cation filed by myself and Michael A. a pneumatic tire, and havin a tubular dia- Kennedy in the United States Patent Oflice phragm of pliable air-tig t fabric con- August 8, 1925. structed and arranged to be movable in an The object of the present improvement is to endwise direction only in complete response provide the type of pressure gauge described to variations in air pressure, a movable rack in the application and characterized by a tumember actuated by said endwise movement bula-r diaphragm of inelastic but pliable maof the diaphragm, said rack member having terial, constructed and arranged to have constant intermeshing engagement with a movement in an endwise direction only topinion which actuates a dial indicator, the

actuate a suit-able pressure indicator in corrack and pinion being movable b the dia respondencc with the air pressure within the phragm in one direction only, an being retire. The present improvement, instead of turnable to initial position after the diausing an air-trapping valve for confining the phragm has retracted from pressure-indicatair within the casing or diaphragm chamber, ing position. f

employs a pressure indicator device actuated These and other features of the invention in one direction only by the diaphragm so will be described in the following specificathat the diaphragm, when retracting to initial tion and will be defined in the claims hereto position, after removal of the gauge from the annexedc tire stem, does not distu b the setting or in- In the accompanying drawings I have 25 dicating position of the indicator mechanism illustrated two forms of constructlon and ar:

' to adapt it to return to its initial position rangement embodying the principles of this after the diaphragm has been restored to invention, in which;

inital position and the reading of the indi- Figure 1 is a rear elevation of a pressure cator has been noted. gauge, the casing being partly cut away to Heretofore it has been proposed, in certain expose the interior of the indicator mechatypes of gauges, to use a ratchet and pawl' nism. construction in conjunction with a Bourdon Figure 2 is a central section taken at a plane tube as a pressure-responsive member for at right angles to the plane of Figure 1 showactuating a pointer for retaining it in presing the'relation of the collapsible diaphragm 35 sure indicating position, but in practice such ;to the indicator mechani m, a 8 devices are found to be so delicate that they Figure 3, is a view similar to Figure 2 will not maintain their accuracy after being showing a modified construction and .arrangetossed about and tumbled over in any automent of diaphragm and indicating mechamobile tool kit for a'short period. Morenism.-,

- 9 over, to get any fine calibration of the pres- Figure4 is a view similar to Figure 1 of sure, such as is desired for balloon tires the same modification showing the indicator where it is desired to register readably and acmechanism and special means for returning it curately differences of only a pound pressure, to initial position after use.

the ratchet wheelmust be made with such Having reference particularly to the form fine teeth that it is easy-for the pawl to beshown in Figures 1 and 2,Ihave shown aholcome disengaged. Other types of 7 gauges low casing 1 providedwith an air inlet pasmaking use of a distensible elastic tube, or of sage 2, leading from the connecting'nipple or a closely packed air piston, are too inaccurate pressure seat 3 which is adapted to be pressed to indicate the slight variations in pressure upon the open end of the valve stem to unseat 59 required for testing balloon tires. the valve and allow communication between the interior of the tire and the interior of the gauge casing, in a well lmown manner.

The end of the casing opposite to the inlet port .is normally closed by a threaded cap 4 tightly screwed upon the open end portion of the casing, and in this case,.pinching between itself and the casing, a peripheral flange 12 ,of a tubular diaphragm 11 having a closed end 13, and having. its peripheral wall formed in annular folds or convolutions to render it extensible and contractible in an endwise direction without the necessity of making the dia-- of the diaphragm, serve to support the outwardly turned folds thereof against collapsing movement.

The casing cap 4 is proyided with a tubular extension 4* which projects into a fiat circular casing 6 containing the indicator mechanism. This casing is provided with a transparent front plate and an interior dial plate 8 over which is moved the pressure-indicating dial pointer 9, which is actuated .by the devices now to be described.

Inside of the tubular extension 4 is located a two-part plunger comprising an outer sleeve "20 and an inner member in the form of a rod v ternally threaded 21, screw-threaded at its lower end, and having adjustable connection with the sleeve 20 by means of an adjustable externally and innut 22. The pitch of the screw threads at the lower end of the rod 21 and of the internal threads at the lower end of the sleeve 20 are identical so that the nut may be screwed upward on the rod to adjust the tension of the resistance spring 24 without varying the relative positions of the rod 21 and the sleeve 20 when both of these members are held against turning. On the other hand, the sleeve 20 may be turned While the nut is held against turning to-lengthen or shorten the effective length of this compound plunger in order to make proper adjustment of the dial pointer without changing the .spring tension.

The plunger 21 actuates the rotatable arbor not by direct engagement, but'by means of an intermediate rack member which, in this case, is; shown as a reciprocatory rack-bar 25 whose teeth intermesh with a pinion 10 on the arbor or shaft 10, and whose lower end has bearing engagement inside a flanged thrust sleeve 26, which right hand side,

vforms a bearing guide for the upper end of the plunger rod 21 and the lower end of the rack-bar member 25 to preserve their alignment with each other and prevent either of their adjacent ends from being caught against the helical resistance spring 24.

The plunger rod 21 is slabbed oil on the as shown in Figure 2, to prevent any vacuum suction on the rack-bar plun er when theplunger 21 is retracted. It will %e understood that the plunger 21 acts purely as a pusher or thrust actuator, and as soon as the connection with the,interior tire is broken, allows the confined air in the cas ingto escape through the port 3 so that the diaphragm is returned to initial position by the resistance s ring 24. This leaves the rack member 25, w ich is with the indicator-actuating pinion 10, stationary in the positions to which they have been moved by the thrust of the movable pressure-responsive diaphragm.

As the rack element is of light construction I prefer to add to its weight somewhat, and this is done in the form hown by means of an attached weight 26 forming, to all practical intents, a part of the rack member so that, by a sudden jerk or blow in an 'endwise' direction, the rack-bar may return to its initial position after the diaphragm has retracted to its initial position. A guide-screw 27 may be secured inner end projecting into a slot in the sleeve 20 to prevent creeping or accidental rotation of the sleeve, and limit the endwise movement of the sleeve induced by the counter-balancing action of the air and spring.

To give a slight frictional resistance that will be insufiicient to impair the practical accuracy of the device, while at the same time preventing the accidental return movement of the rack-bar member if it becomes loose in' its bearing sleeve, I provide a spring-pressed ball 25 mounted in a recess in the lower end of the rack-bar to frictionally engage the sleeve 26iwith a light pressure.

. In the alternative embodiment of the invention shown in Figures 3 and 4, the lower part of the casing which is'applied to the ency will be for the diaphragm to expand in.

every direction. Therefore, supporting rings 15 are placed around the outside of the outward folds or convolutions to confine the conpermanently in mesh in the casing extension 4 with its.

folds, at their exterior concave surfaces, are

held against lateral displacement by means of the rings 16. a

Over the closed end of the diaphragm, is

placed a flat thrust disk 17, which is prevented p from lateral displacement by the topmost ring 15. On this thrust plate 17 rests a compound plunger comprising the sleeve 20 and the internal rod 21 with the tensioningthrust nut 22, just as above described, which supports the counterbalancing thrust 'of t 6 spring 24, all mounted within the upward tubular extension 31 of the cap the casing. This tubular mem er '31 is vertically slotted on one side and provided with a pair of spaced projecting cars 32 through which is passed a rotatable pin 33, to which is secured a rack element .34: of sector shape whose arcuate series of. teeth constantly in-. termesh with the pinion 10 on the arbor 10, which carries the dial indicator pointer 9, as

. above described.

upward, rotating the Thissector-shaped rack element is formed to engage the upper end of the pressure-responsive plunger 21 so that when the plunger moves upward the rack-element is also moved pinion according to the travel of the plunger-rod 21 which is proportionate to the pressure exerted against the endwise movable diaphragm. If desired frictional retardation, similar to that already described, may be provided by a set-screw 35 pressing a small spring against one end of the indicator arbor 10 to give a slight friction thereon.

The rack and pinion elements may be returned to initial position by means of a pivotally connected bar 36 carryinga weight 37, secured at a proper distance from the bearing ortion 38 of the casin i0 to prevent the rack item being accidental y moved out of intermeshing relation to the pinion. This stop member 37 also may serve as a-weight for restoring the indicator parts to initial position, and at the same time, as shown in the drawings, the rod is projected far enough outside of the casing to permit initial pressure thereon by the finger to restore it to initial position.

In both forms illustrated the action is effected through a diaphragm element that, unlike a tight-fitting piston, is substantially free from friction and absolutely free from leakage so as to make it very sensitive to changesin pressure, while leaving nothing to get out of order, and it is not affected, as

Y stretchable elastic diaphragms are, by change in condition of the distensible rubber. -At the same time the indicator portion of the mechanism is completely responsive to slight endwise movement of the diaphragm which it indicates on a greatly enlarged scale so as to afford easy reading of small variations in pressure, which is particularly desirable in ortion 30 of the case of a tire pressure gauge for balloon tires. The slight frictional retardation of the indicator mechanism is altogether too small to impair the accuracy of the indicator,

while being entirely adequate to preserve the ressureindication unt1l it is read. The adjustment provisions are such that the tensioning of t e spring to afiord the proper counterbalancing resistance may be effected, and the proper correspondence between the dial reading and the actual pressure may brought about with, the greatest. accuracy. Both the pressure-responsive diaphragm and the transmission mechanism for actuating the dial. indicator are of such construction that there is nothing to get out of order under the rather rough handling vices are commonly subjected.

What I claim is; 1. In a pressure gauge for testing pneumatic tires, the combination with a hollow casing provided with an air inlet to admit" an air-confining tubular dia-' compressed air, phragm of pliable air-tight fabric formed with annular convolutions and a closed end wall, the open end of said diaphragm being secured inside the casing to expose its interior to the air admitted into the casing, ex

ternal ineans engaging the exterior convexpermit expansion and contraction in an endwise direction,- separate external confining members engaging'the convex and the concave surfaces of the annular convolutions to prevent lateral expansion, a dial pressure indicator, a movable actuator moved in one direction only in correspondence with the endwise movement of the diaphragm, and means by which the indicator may be returned at will to initial position after the diaphragm has retracted.

3. In a tire pressure gauge, tion of a pressure responsive tubular diaphragm movable in an endwise direction only against a counterbalancing spring, a dialpressure indicator, a spring-resisted plunger adjustable as to length opposing a yielding resistance to the endwise pressure-induced movement of the diaphragm, a toothed rack member movable outwardly by the movement of said plunger and having continuous operative connection with the dial-indicator to the combinato which such deing movement pressure-indicating posi-- tion, and means for returning said rack member and indicator to initial position independently of the return movement of the diaphragm.

4. In a tire pressure gauge, the combinamove it to and from tion of a spring-resisted endwise movable airconfining tubular diaphragm, a rack member arranged to be pushed outwardly by the end wise movement of the diaphragm and returnable to initial position independently of the diaphragm, 'a dial-pressure indicator operatively connected moved thereby in both directions through an intermeshing pinion, and means for preventof the rack member out of engagement with the pinion and for effecting ing the relationship the return of the rack member and the indicator to initial position.

5. In a tire pressure gauge, thecombination of an endwise movable air-actuated spring-resisted diaphragm, a dial pressure indicator, an indicator actuator having movement responsive to the endwise movement of the diaphragm in one direction only, and having rack and pinion connection with the pressure indicator, and means for exerting a slight but-constant retarding friction on the rack member to prevent accidental movement of the rack member.

-6. In a tire pressure gauge, the combination with'a pressure-responsive diaphragm movable against a counterbalancing spring resistance, a rack and pinion actuated dial pressure indicator, and means intermediate of the diaphragm and the indicator for varybetween the diaphragm and the indicator to effect accurate corre spondence between the pressure-responsive position of the diaphragm and t e pressure indicator,.while preserving the intermeshing relation between the rack and pinion.

In witness whereof, I have subscribed the above specification.

I JOHN E. HNNEDY,

with said rack member to be 

